#include<stdlib.h>
#include<stdio.h>

int main(int argc,char*argv[],char*env[])
{
    printf("env from main:\n");
    for(int i=0;i<5;i++)
    {
        printf("%s\n",env[i]);
    }
    printf("\n");

    extern char**environ;
    printf("env from extern:\n");
    for(int i=0;i<5;i++)
    {
        printf("%s\n",environ[i]);
    }

    printf("\n env from getenv:%s\n",getenv("HISTSIZE"));
    return 0;
}
